Published version [Abstract:]Reductions in body size are increasingly identified as a response to climate warming. Here we present evidence for a case of such body shrinkage, potentially due to malnutrition in early life. We show that an avian long-distance migrant (red knot Calidris c. canutus), experiencing globally unrivaled warming rates at its high-Arctic breeding grounds, produces smaller offspring with shorter bills during summers with early snowmelt. This has consequences half a world away where short-billed individuals have reduced survival on their tropical wintering grounds. This is associated with these molluscivores eating fewer deeply buried bivalve prey and more shallowly buried seagrass rhizomes. We suggest seasonal migrants experience reduced fitness at one end of their range due to a changing climate at the other end. Published version 3Phenological changes and geographical range shifts represent well-known responses to climate change (1). A third broadly observed response to global warming appears to be shrinkage of bodies (2-5). It has been hypothesized that body shrinkage is a genetic micro-evolutionary response to warming due to smaller individuals being better able to dissipate body heat due to a larger body surface/volume ratio (e.g., Bergmann's rule (2)). Conversely, it has been put forward that climate change may disrupt trophic interactions, potentially leading to malnutrition during an organism's juvenile life stage (6, 7). As poor growth may not be compensated for later in life (8), this would lead to smaller bodies (i.e., shrinkage as a phenotypically plastic response).Under climate change, some regions are warming up faster than others. Especially in the Arctic, warming has been observed at unprecedented rates (9, 10). Hence, body-size reductions would be expected to be most pronounced in the world's most northerly region (6). Many Arctic-breeding avian species, however, are long-distance migrants spending the northern winter at lower latitudes (11), where the impacts of climatic change are less obvious.Here, based on the analysis of satellite data, we show that over the past 33 years, snowmelt has occurred progressively earlier on the high-Arctic breeding grounds of the red knot (Calidris canutus canutus) at Taimyr Peninsula ( Fig. 1; 76-78°N), changing at a rate of about half a day per year ( Fig. 2A; R 2 = .32, F1,31 = 14.77, P < .001; see Table S1 and Figs. S1-S3). During these three decades, 1,990 juvenile red knots were caught and their body sizes measured in Gdańsk Bay, Poland, during their first southward migration to the West-African nonbreeding grounds (Fig. 1). These juvenile birds were smaller after Arctic summers with an early snowmelt, notably with respect to body mass ( Fig. 2B; AIC c = 14775.24, P < .0005; Table S2), bill length ( Fig. 2C; AICc = 7610.48, P < .005; Table S3), and overall body size (PC1 on bill, tarsus, and wing; Table S4; AICc = 5925.22, P < .05). The models best explaining variation in bill length and overall body size additionally included breedin...

Migration is an energetically expensive and hazardous stage of the annual cycle of non‐resident avian species, and requires certain morphological adaptations. Wing shape is one of the morphological traits that is expected to be evolutionarily shaped by migration. Aerodynamic theory predicts that long‐distance migrants should have more pointed wings with distal primaries relatively longer than proximal primaries, an arrangement that minimizes induced drag and wing inertia, but this prediction has mostly been tested in passerine species. We applied the comparative method of phylogenetically independent contrasts to assess convergent evolution between wing shape and migration within shorebirds. We confirmed the assumption that long‐distance migrants have less rounded wings than species migrating shorter distances. Furthermore, wing roundedness negatively correlates with fat load and mean distance of migratory flights, the basic components of migration strategies. After controlling for interspecific differences in body size, we found no support for a link between wing length and migration, indicating that wing shape is a more important predictor of shorebird migratory behaviour than wing length. The results suggest that total migration distance and migratory strategy may simultaneously act on the evolution of wing shape in shorebirds, and possibly in other avian species.

Zehtindjiev P., Ilieva M., O¿arowska A., Busse P. 2003. Directional behaviour of the Sedge Warbler (Acrocephalus schoenobaenus) studied in two types of orientation cages during autumn migration a case study. Ring 25, 1-2: 53-63.Migratory directions of Sedge Warblers tested in the Emlen funnel and Busses flat cage during autumn migration in the Balkan region were studied. Some methodological aspects of orientation data analysis were discussed as well. According to orientation data at least two populations of the Sedge Warbler migrate in NE Bulgaria: one in SW direction via Greece, crossing the Mediterranean Sea to Libya, and then Central Africa and second one through Turkey, (Cyprus?) and the Middle East to the eastern parts of winter quarters (SE direction). This pattern is clear when a calculation method that assumes reverse and axial behaviour of birds (i.e. reversing vectors from northern sectors) is applied. Nature of reverse migration is still not well recognised and seems to be very interesting for further studies.

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SUMMARYCircular orientation cages have been used for several decades to record the migratory orientation of passerine migrants, and have been central to the investigation of the functional characteristics of the biological compasses used for orientation. The use of these cages offers unique possibilities to study the migratory behaviour of songbirds, but suffers from statistical limitations in evaluating the directions of the activity recorded in the cages. The migratory activity has been reported to vary, including complex multimodal orientation of migratory passerines tested in orientation cages irrespective of species studied. The currently applied circular statistical methods fail to describe orientation responses differing from unimodal and axial distributions. We propose for the first time a modelling procedure enabling the analysis of multimodal distributions at either an individual or a group level. In this paper we compare the results of conventional methods and the recommended modelling approach. Migratory routes may be more complex than a simple migratory direction, and multimodal behaviour in migratory species at the individual and population levels can be advantageous. Individuals may select the expected migratory direction, but may also return to safer sites en route, i.e. sites already known, which provide food and/or shelter in reverse directions. In individual birds, several directions may be expressed in the same test hour. At the species level, multimodal orientation may give an opportunity to expand the range or may refer to differential migration route preferences in different populations of birds. A conflicting experimental situation may also result in a different preferential orientation. In this paper we suggest a statistical solution to deal with these types of variations in orientation preference.